Sleep is a physical and mental resting state in which a person becomes relatively inactive and unaware of the environment. In essence, sleep is a partial detachment from the world, where most external stimuli are blocked from the senses.
Normal sleep is characterized by a general decrease in body temperature, blood pressure, breathing rate, and most other bodily functions. In contrast, the human brain never decreases inactivity. Studies have shown that the brain is as active during sleep as it is when awake. Throughout an eight-hour sleep cycle, a normal adult alternates between two very different states, non-REM and REM (Rapid Eye Movement) sleep. Sleep is characterized by two distinct states, non-REM sleep and REM sleep. Non-REM and REM sleep alternate in 90- to 110-minute cycles. A normal sleep pattern has 4-5 cycles. The diagram and descriptions below illustrate the architecture of sleep. This explains why the cycles of sleep have been compared to going up and down a stairway.
The five-step sleep cycle repeats itself throughout a night of sleeping, much like a roller coaster. As a person drifts off, Stage 1 begins. After a few minutes, the EEG deteAs children develop, both the distribution of sleep in a 24-hour period and total sleep requirements change. A newborn infant requires 16 to 18 hours of sleep a night, decreasing to 14 or 15 hours by age one, 10 or 12 by age four, and less than 10 by age ten. Sleep needs further decrease as adolescence progresses, stabilizing at 7 or 8 hours in adulthood. The elderly tend to lose their capacity for extended sleep. They may sleep very little at night but doze during the day, returning to the multiphasic sleep patterns of childhood.cts sleep. It may take anywhere from 30 – 40 minutes to cycle through Stage 2 through 4. Now, an individual backtracks through Stage 3, then Stage 2, and finally into REM sleep. This occurs 4 - 5 times per night. Six to eight hours per day is the average amount of sleep a person...
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